Acoustic Dampening Compensation System

ABSTRACT

At least one exemplary embodiment is directed to a communication device that includes a microphone configured to detect an acoustic signal from an acoustic environment, and a processor, configured to detect an acoustical dampening between the acoustic environment and the microphone, based on a change in a characteristic of the acoustic signal and, responsive to the acoustical dampening, apply a compensation filter to the acoustic signal to form a compensated acoustic signal that is reproduced. Other embodiments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/109,987, filed on Dec. 18, 2013, which is a continuation of andclaims priority to U.S. patent application Ser. No. 12/044,727, filed onMar. 7, 2008, now U.S. Pat. No. 8,625,812, which claims priority to andthe benefit of Provisional Application No. 60/893,617, filed on Mar. 7,2007, all of which are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates to acoustic signal manipulation, and moreparticularly, though not exclusively, to the acoustic compensation ofacoustic dampening by headwear on detected acoustic signals.

BACKGROUND OF THE INVENTION

Some acoustic detecting and/or measuring devices (e.g., earpieces, roommicrophones), that measure ambient acoustic signals can be adverselyaffected when an acoustic dampening occurs between the source of anacoustic signal in an environment and the detecting and/or measuringdevice. The effect can be frequency dependent and can adversely effectthe quality (e.g., spectral characteristics) of the measured acousticsignal.

SUMMARY OF THE INVENTION

In a first embodiment, a communication device includes a microphoneconfigured to detect an acoustic signal from an acoustic environment,and a processor, configured to detect an acoustical dampening betweenthe acoustic environment and the microphone, based on a change in acharacteristic of the acoustic signal and, responsive to the acousticaldampening, apply a compensation filter to the acoustic signal to form acompensated acoustic signal that is reproduced. In one arrangement, thecompensation filter can approximate an inverse of the acousticaldampening between the acoustic environment and the microphone. Themicrophone can be operatively and communicatively coupled to headwear,where the processor, responsive to an analysis of the change in thecharacteristic of the acoustic signal, can detect a presence of theheadwear. The processor, from the analysis, can detect when the headwearis worn or removed, and apply the compensation filter to accommodate theheadwear based on the presence of the headwear.

The processor can selectively adjust the spatial sensitivity of theheadwear to sound in the user's local environment. The headwear can beone of a headset, earbud, earpiece or combination thereof. And, theprocessor actively detects when headwear is adjusted or fitted; it canbe activated on a continuous or intermittent basis. In one arrangement,the compensation filter for the headwear can be activated viavoice-activation. As an example, the processor detects an onset of theacoustical dampening from a first acoustic signal and responsive to thedetected onset of the acoustical dampening applies the compensationfilter. The communication device can be a portion of one of a computersystem, a personal digital assistant, a cellular phone, a mobile phone,an earpiece or a head-worn communication device.

In a second embodiment, a method of compensating for acousticaldampening includes the steps of detecting an acoustic signal from anacoustic environment via a microphone, and detecting an acousticaldampening between the acoustic environment and the microphone based on achange in a characteristic of the acoustic signal, and, responsive tothe acoustical dampening, filtering the acoustic signal using acompensation filter approximating an inverse of the acoustical dampeningbetween the acoustic environment and the microphone. The microphone canbe operatively coupled to headwear, and the processor, responsive to thechange in the characteristic of the acoustic signal, detects a presenceof the headwear. The headwear can be worn or removed, and apply thecompensation filter to accommodate the headwear based on the presence ofthe headwear.

The processor can apply the compensation filter to selectively adjust aspatial sensitivity of the headwear to sound in the acousticenvironment. The headwear can be one of a headset, earbud, earpiece orcombination thereof. The processor can actively detect when headwear isadjusted or fitted; it can be activated on a continuous or intermittentbasis. In one configuration, the compensation filter for the headwearcan be activated via voice-activation. The processor can detect an onsetof the acoustical dampening from a first acoustic signal and responsiveto the detected onset of the acoustical dampening apply the compensationfilter. The communication device can be a portion of one of a computersystem, a personal digital assistant, a cellular phone, a mobile phone,an earpiece or a head-worn communication device.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of present invention will become more fullyunderstood from the detailed description and the accompanying drawings,wherein:

FIG. 1A illustrates one example of an acoustic dampening compensationdevice;

FIG. 1B illustrates one example of a situation of an acoustic dampeningelement affecting an acoustic signal;

FIG. 2A is a flow chart of an acoustic compensation system according toat least one exemplary embodiment;

FIG. 2B is a block diagram of a microphone signal conditioner;

FIG. 3A illustrates at least one method of detecting whether an acousticdampening event occurs in accordance with at least one exemplaryembodiment;

FIG. 3B illustrates at least one further method of detecting whether anacoustic dampening event occurs in accordance with at least oneexemplary embodiment;

FIG. 4A illustrates at least one further method of detecting whether anacoustic dampening event occurs in accordance with at least oneexemplary embodiment;

FIG. 4B illustrates a user voice spectral profile acquisition system inaccordance with at least one exemplary embodiment;

FIG. 5A illustrates a block diagram of a parameter look up system inaccordance with at least one exemplary embodiment;

FIG. 5B illustrates a headwear equalization system in accordance with atleast one exemplary embodiment; and

FIG. 6 illustrates an example of detecting a drop in sound pressurelevels using the rate of change, mean values, slopes and otherparameters in accordance with at least one exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION

The following description of exemplary embodiment(s) is merelyillustrative in nature and is in no way intended to limit the invention,its application, or uses.

Exemplary embodiments are directed to or can be operatively used onvarious wired or wireless earpieces devices (e.g., earbuds, headphones,ear terminals, behind the ear devices or other acoustic devices as knownby one of ordinary skill, and equivalents).

Processes, techniques, apparatus, and materials as known by one ofordinary skill in the art may not be discussed in detail but areintended to be part of the enabling description where appropriate. Forexample specific computer code may not be listed for achieving each ofthe steps discussed, however one of ordinary skill would be able,without undo experimentation, to write such code given the enablingdisclosure herein. Such code is intended to fall within the scope of atleast one exemplary embodiment.

Additionally exemplary embodiments are not limited to earpieces, forexample some functionality can be implemented on other systems withspeakers and/or microphones for example computer systems, PDAs,BlackBerry® smartphones, cell and mobile phones, and any other devicethat emits or measures acoustic energy. Additionally, exemplaryembodiments can be used with digital and non-digital acoustic systems.Additionally various receivers and microphones can be used, for exampleMEMs transducers, diaphragm transducers, for example Knowles' FG and EGseries transducers.

Notice that similar reference numerals and letters refer to similaritems in the following figures, and thus once an item is defined in onefigure, it may not be discussed or further defined in the followingfigures.

At least one exemplary embodiment of the present invention isillustrated in FIG. 1A. The embodiment is a small headphone that isinserted in the ear of the user. The headphone consists of thesound-attenuating earplug 100 inserted into the ear. At the inner(eardrum-facing) surface of the earplug 100, an ear-canal loudspeakerreceiver 102 is located for delivering an audio signal to the listener.At the outer (environment-facing) surface of the earplug 100, anambient-sound microphone 104 is located. Both the loudspeaker 102 andthe microphone 104 are connected to the electronic signal processingunit 106. The signal processing unit 106 also has a connector 108 forinput of the audio signal. Additionally, an ear-canal microphone 110 isplaced at the inner (eardrum-facing) surface of the earplug 100 and anexternal loudspeaker 112 is placed on the outer (environment-facing)surface of the earplug 100 for performing other functions of theheadphone system not described here (such as monitoring of soundexposure and ear health conditions, headphone equalization, headphonefit testing, noise reduction, and customization).

FIG. 1B illustrates an example of an acoustic dampening element 120 a,moving 140 a into the path of an acoustic signal or wave 130 a generatedby an acoustic source 100 a in ambient environment. The acoustic signalor wave 130 a can be acoustically damped to some level by acousticdamping element 120 a, so that the acoustic signal measured by themicrophone 110 a is effected.

FIG. 2a depicts a general “top-level” overview of the Headwear acousticEqualization System (HEQS). Initialization of the HEQS 142 may bemanually invoked in a number of ways. One way is a manual activation; byeither the HEQS user (i.e. that person wearing the headset system inFIG. 1A), or manually by a second person in a local or remote location(e.g. a supervisor). Another activation method is with an automaticmode, for instance in response to a loud sound or when the user donsheadwear (e.g. a helmet). There are a number of methods for detectingheadwear, as disclosed by the systems in FIGS. 3a and 4a . When headweardetection systems determine that headwear is worn, then decision unit101 invokes a system 103 to determine the frequency dependent acoustictransmission index of the headwear (ATI_HW). An inverse of ATI_HW(inverse ATI_HW) 105 is calculated. The method for determining ATI_HW isdescribed in FIGS. 5a and 5b . The ASM signal is then filtered 107 witha filter with a response approximating the inverse ATI_HW 105. Thisgives a modified ASM signal which approximates that the ASM signal withthe headwear removed. The filter system 107 may use entirely analogcircuitry or may use digital signal processing, e.g. using an FIR-typedigital filter. Depending on the particular operating mode of the HEQSthe ATI_HW may be updated on a continuous or intermittent basis, asdetermined by decision unit 109. If the operating mode is such thatATI_HW is calculated just once, then the update sequence is terminated111.

FIG. 2b describes an optional beam-forming platform 138. The beamforming platform 138 allows for the direction-dependent sensitivity ofthe microphones in the headset in FIG. 1 to be electronicallymanipulated. For instance, the sensitivity may be increased in thedirection of the HEQS user's voice, and decreased in the direction oflocal noise sources, such as machine noise. The beam-forming platform138 takes as its inputs at least three Ambient Sound Microphones (ASMs)114, 122, 130. The analog signal is then amplified (amp) 116, 124, 132,and then filtered with a Low Pass Filter (LPF) 118, 126, 134 to preventfrequency aliasing by the Analog to Digital Converters (ADC) 120, 128,136. The beam-forming platform 138 may also take as its input signal theoutput signal from ASMs in both the left and right headsets worn by theHEQS user. The output signal 140 for each headset is considered the“conditioned ASM signal” in other figures in the present invention.

FIG. 3a depicts the SONAR-based headwear detection platform. This systemdetects the presence of headwear using a SONAR-based system. Activationof this system 142 may be manually by a remote second person 144 or bythe HEQS user 141, or may be automatic 140 e.g. with a computer timer. ASONAR test signal is reproduced with the External Receiver (ER) 112whilst simultaneously recording 143 the conditioned ASM signal 148. TheSONAR test signal 145 may be one of a number of specific test signals,as described in FIG. 3b . The recorded ASM signal 143 is analyzed 146 toextract the time-domain impulse response (IR) or frequency domaintransfer function 150. The frequency-domain transfer function may beobtained empirically by dividing the spectral frequency profile of theSONAR test signal 145 by the spectral frequency profile of the recordedASM signal 143 (if the spectral frequency profile is logarithmic, thenthis would be a subtraction of the two profiles). Alternatively, anadaptive filter such as one based on the LMS algorithm may be used toiteratively approximate the time-domain impulse response or frequencydomain transfer function. If a maximum-length sequence (MLS) SONAR testsignal is used, then the time-domain IR may be obtained bycross-correlation of the MLS and recorded ASM signal 143. The resultingIR is then analyzed to detect headwear. This is undertaken by detectingfeatures in the IR representative of strong sound reflections at timedelays consistent with headwear; for instance, if a helmet is worn, thena reflection from the brim is expected at about 0.6 ms for a brim thatis 10 cm from the headset. If close-fitting headwear is worn, such as abalaclava or fire-proof hood, then a higher-level IR would be observed(especially at high frequencies) compared with the case when no headwearis worn. If no headwear is worn, then decision unit 152 determines thatno additional filtering of the ASM signal is undertaken 154. However, ifthe analysis of the obtained IR 146 predicts that headwear is worn, thendepending on the particular operating mode 156 (which may be set withthe initialization system 142) filtering of the ASM signal may beinvoked with either a look-up table based EQ system (FIG. 5a ) or avoice-based EQ system (FIG. 5b ).

FIG. 3b depicts the assembly for generating the SONAR test signal usedby the SONAR-based headwear detection platform in FIG. 3b , and also forthe system which determines the acoustic transmission index of theheadwear described in FIG. 5a . When the SONAR test signal is needed,the activation command 158 initializes a counter 160 which keeps arecord of the number of repetitions of the test stimulus (i.e. how manyaverages the analysis system makes). The particular test signal used maybe one of a number of signals; a frequency sweep 164 (ideally thisso-called chirp signal is from a lower frequency to a higher frequencywith a logarithmic rather than linear incremental sweep). Single ormulti-frequency sine-waves may also be used to give afrequency-dependent acoustic transfer function. A Maximum LengthSequence (MLS) signal 166 is often used to measure acoustic impulseresponses. Transient (Dirac) impulses 168 give a IR directly. Musicaudio 170 may be used to measure the transfer function, as well as noisebursts 171 which may be narrow-band filtered. Once the audio test signalis acquired 162, the signal is sent 172 to the external receiver (ER)112 via digital to analog conversion (DAC) 174 and analog amplification(amp) 176 (which may be frequency-dependent to compensate for theelectroacoustic sensitivity of the loudspeaker). A digital counter 180tracks the number of times the audio test signal is repeatedlyreproduced with the ER, and decision unit 182 terminates reproduction ofthe test signal 184 when the number of repeats is sufficient.

Alternative to the SONAR-based system in FIG. 3a is the Voice-basedheadwear detection platform described in FIG. 4a . This system detectsthe presence of headwear using a user-generated voice. Activation ofthis system 142 may be manually by a remote second person 144 or by theHEQS user 141, or may be automatic 140 e.g. with a computer timer. Theheadwear is detected by analyzing the conditioned ASM signal 148 inresponse to user-generated voice 186. The prompting system for the userto speak is described in FIG. 4b . The recorded ASM signal is analyzedby unit 143 when there is no headwear present to give a reference uservoice spectral profile 187. When the user dons headwear, they areprompted to speak (see FIG. 4b ) and a second ASM recording is made togive a current user voice spectral profile 188. The reference user voicespectral profile 187 and current user voice spectral profile 188 arecompared with unit 189 to give a transfer function which is analyzed topredict if headwear is worn. This analysis system may, for instance,determine that headwear is worn if the transfer function indicates thathigh-frequency content (e.g. at particular frequencies such as 1 kHz and4 kHz) are attenuated in the current user voice spectral profile 188compared with the reference user voice spectral profile 187 (e.g. are <5dB at these particular frequencies). If this analysis unit 189determines that headwear is not worn, then decision unit 152 does notfilter the ASM signal 154. Alternately, if analysis unit 189 determinesthat headwear IS worn, then decision unit 152 further determines thefrequency dependent acoustic transmission index of the headwear (ATI_HW)that is used to filter the ASM signal (i.e. with a filter responseapproximating the inverse of ATI_HW). ATI_HW is calculated depending onthe particular operating mode, as determined by unit 156. These twooperating modes are described in FIG. 5a and FIG. 5 b.

FIG. 4b describes the user-prompting system for the voice-based headweardetection platform. Activation command 190 initializes a counter 191which keeps a record of the number of repetitions of the test stimulus.Either a pre-recorded verbal message 192 or non-verbal message 194 (e.g.a tone) is acquired 193 as a prompt message. The prompt message sent 172to external receiver 112 (after digital to analog conversion 174 andanalog amplification 176) and is reproduced with the External Receiver112 for the user to speak either a specific set of words (e.g. aphonetically balanced word list) or general words (e.g. normalconversation) or non-speech sounds (such as a whistle or hand-clap).This prompt may be repeated a number of times, according to theincremental repeat counter 196 and decision unit 198 which terminates200 the prompt message after a pre-defined number of repeated messageprompts.

FIG. 5a describes a system for determining the acoustic transmissionindex of the headwear (ATI_HW). This is a frequency dependent value forthe free-field acoustic absorption of the headwear from an externalsound source to a measurement point on the other side of the headwear(specifically, measured at the entrance to the user's ear canal). Thesystem uses the SONAR headwear detection platform described in FIG. 3ato obtain a headwear impulse response 150. It should be noted that thisis not the same as the ATI_HW; rather, it is the impulse responseobtained by emitting a SONAR test signal from the external receiver (112in FIG. 1) and recording the sound response at the ASM 104 (orconditioned ASM signal 140 in FIG. 2b ). In a particular optional learnmode 202, the IR of different headwear may be measured empirically, andtheir corresponding ATI_HW is also measured and stored in computermemory 204. The recently measured headwear IR 150 is then compared andmatched with measured IRs in the database 204 using matching unit 206(matching may be accomplished using a standard least mean squaresdifference approach). When the current headwear has been matched to onein the database, then the ASM signal 140 is filtered with an impulseresponse (or frequency-domain transfer function) which approximates theinverse of the matched ATI_HW 208. The filtering of the ASM signal byunit 210 may be accomplished using a digital FIR-type filter or anIIR-type digital filter, or a multi-band analog audio signal filter.Depending on the particular operating mode of the HEQS selected by theuser (or automatically selected) with selecting device 212, the ATI_HWmay be continually updated by decision unit 214. The process may beterminated at step 216.

FIG. 5b describes an alternative method to that system in FIG. 5a , fordetermining the ATI_HW of the headwear worn by the HEQS user. The methodin FIG. 5b begins at step 218 and uses a measure of the user's referencevoice spectral profile 187. This is a spectral profile of the(conditioned) ASM signals when no headwear is worn in response touser-generated speech or non-speech (e.g. hand-claps). This is comparedto the current ASM spectral profile 188 when the user is wearingheadwear. The comparison is undertaken by unit 189, which may be asimple spectral subtraction (in the logarithmic or decibel domain), ormay be a division of the linear spectral magnitude. The resultingtransfer function approximates ATI_HW, and its inverse is calculated byunit 220 to give a data vector which can be used to filter the ASMsignals with filter unit 210 (as previously described for FIG. 5a ). Theprocess may be terminated at step 216.

FIG. 6 illustrates an acoustic signal 600 displayed in a non-limitingmanner as the sound pressure level versus time, t. In this non-limitingexample acoustic signal 600 is broken into three regions. The firstregion can be characterized by an average value SPL-M1, with anassociated baseline (e.g., a line fit utilizing least squares) having aslope SLP-1. Similarly the second and third regions can be characterizedby an average value SPL-M2 and SPL-M3 respectively, with an associatedbaseline (e.g., a line fit utilizing least squares) having slopes SLP-2and SLP-3 respectively. FIG. 6 illustrates the situation where amicrophone (throughout the duration) is measuring the acoustic signal600, the measurement plotted in FIG. 6. At the onset of an acousticdampening event (e.g., sheet placed on microphone, headwear placed overearpiece microphone) the measured Sound Pressure Level (SPL) valuedecreases from SPL-M1 to SPL-M2 over a period of time Dt1. The rate ofdecrease, [(SPL-M2)−(SPL-M1)]/Dt1=R1, can be compared to a thresholdvalue T1 to aid in determining if an acoustic dampening event hasoccurred. For example if R1=20 dB/1 sec, and T1=10 dB/sec, and thecriteria for an acoustic dampening effect (e.g., rather than an acousticsource shut off) is |R1|<T1, then if |R1|<T1 (note that a criteria R1>T1can also be used as well as an equality relationship) as it is in theexample can be used as an indication of an acoustic dampening eventrather than an acoustic source shut off. Note that in the exampleillustrated in FIG. 6, the acoustic dampening event is removed resultingin an increase from SPL-M2 to SPL-M3 in time Dt2. The rate of change,R2=[(SPL-M3)−(SPL-M2)]/Dt2, can be compared with a threshold T2 in asimilar manner as described above for T1. Another threshold that can beused is the dropped sound pressure levels (DSPL1, DSPL2) averagebaseline value, for example if SPL-M2>SPL-T3 then this can be used as anindication that an acoustic dampening event has occurred rather than anacoustic source shut off. For example if the threshold value SPL-T3 iseffective quiet (e.g., 80 dB) then if SPL-M2 drops to below SPL-T3 thenthis can be indicative of an acoustic source being turned off.

Other criteria can also be used as indicators of an acoustic dampeningevent occurring. For example if the slopes of the baselines before andafter shifting are significantly different this can be indicative of anacoustic source shut off rather than an acoustic dampening event. Forexample if |SLP-2−SLP-1|>|(SLP-1/2)|, this could be indicative that anacoustic source has been turned off and that possibly the slope of thesecond baseline (SLP-2) is close to zero.

FURTHER EXEMPLARY EMBODIMENTS

The following paragraphs list various other exemplary embodiments of theinvention. The list is meant as illustrative only not as a limitativelist of embodiments.

A self-contained Headwear Acoustic Equalization system (HEQS) tocompensate for the acoustic filtering of headwear (hats, helmets,fire-proof headwear etc.) is herein described. The Headwear AcousticEqualization System (HEQS) empirically measures or determines theacoustic filtering properties of a head garment on a continuous,intermittent, or discrete basis. The acoustic filtering properties areused to compensate for the change in response of a microphone mounted onthe user's head (e.g. at or near the entrance to the ear canals) from anexternal sound source (e.g. voice) by filtering the microphone signalwith an audio signal filter (which may be adaptive or one from apre-defined filter database). The HEQS comprises:

-   -   A. An assembly to monitor the acoustic field in a user's        immediate environment using one or more Ambient Sound        Microphones (ASMs) located near to or at the entrance to one or        both occluded ear canals.    -   B. A signal processing circuit to amplify the signals from the        ASMs in (A) and to equalize for the frequency sensitivity of the        microphones and to low-pass filter (LPF) the signals prior to        digital conversion to prevent aliasing (with the cut-off        frequency of the LPF equal or less than half the sampling        frequency of the digital sampling system).    -   C. An analog-to-digital converter (ADC) to convert the filtered        analog signals in (B) to a digital representation.    -   D. An optional beam-forming platform that takes as its inputs        the digital signals from the ASMs from one or both headsets to        selectively affect the spatial sensitivity of the headset to        sound in the user's local environment.    -   E. An assembly to generate a desired SPL at or near the entrance        to one or both occluded (or partly occluded) ear canals        consisting of a loudspeaker receiver mounted in an earplug that        forms an acoustic seal of the ear canal. (This is the External        Receiver; ER).    -   F. A signal processing circuit to amplify the signal to the ER        to equalize for the frequency sensitivity of the transducer.    -   G. A digital-to-analog converter (DAC) to convert a digital        audio signal into an analog audio signal for reproduction with        the ER.    -   H. A HEQS initialization system to start the HEQS; which may be        manually initialized by the user with voice-activation or with a        physical switch, or may include remote activation by a second        person, or may be automatically activated by a system which        detects when headwear is adjusted or fitted, or may be activated        on a continuous or intermittent basis.    -   I. A system to detect whether the HEQS user is wearing headwear.        Examples of headwear include: a military helmet, a SWAT hood,        balaclava, cold-weather face mask, helmet liner, neoprene        camouflage face mask, religious headwear such as a burka or        turban, or a fireproof face mask as typically worn by fighter        pilots and fire-service workers (fire men/women).    -   J. A system to determine the frequency-dependent acoustic        attenuation of the headwear from an ambient sound source (such        as the user's voice or a sound-creating object in the        environment of the user) to the ASM(s). This attenuation        transmission index is called ATI_HW.    -   K. A system to filter the ASM signal with the inverse of the        ATI_HW of the headwear, so as to give an ASM signal similar to        that with the headwear absent.    -   L. A system to update the ATI_HW automatically on a continuous        basis.    -   M. A system to update the ATI_HW manually from either a        user-generated command or a command issued by a second remote        person.    -   N. A system to update the ATI_HW automatically on an        intermittent basis (e.g. every 10 minutes).    -   O. A system to transmit the ATI_HW to a data storage or analysis        system using a wired or wireless data transmission system.

Another embodiment of the invention enables the HEQS to automaticallydetermine if headwear is worn using a self-contained SONAR-basedheadwear detection platform. A SONAR test sound is emitted with anexternal receiver mounted on the headset device, and its soundreflection is detected using one or more ambient sound microphonesmounted on the same headset. The reflected sound is analyzed todetermine the presence of headwear. This SONAR-based headwear detectionplatform comprises:

-   -   A. An assembly to monitor the acoustic field in a user's        immediate environment using one or more Ambient Sound        Microphones (ASMs) located near to or at the entrance to one or        both occluded ear canals.    -   B. A signal processing circuit to amplify the signals from the        ASMs in (A) and to equalize for the frequency sensitivity of the        microphones and to low-pass filter (LPF) the signals prior to        digital conversion to prevent aliasing (with the cut-off        frequency of the LPF equal or less than half the sampling        frequency of the digital sampling system).    -   C. An analog-to-digital converter (ADC) to convert the filtered        analog signals in (B) to a digital representation.    -   D. An optional beam-forming platform that takes as its inputs        the digital signals from the ASMs from one or both headsets to        selectively affect the spatial sensitivity of the headset to        sound in the user's local environment.    -   E. An assembly to generate a desired SPL at or near the entrance        to one or both occluded (or partly occluded) ear canals        consisting of a loudspeaker receiver mounted in an earplug that        forms an acoustic seal of the ear canal. (This is the External        Receiver; ER).    -   F. A signal processing circuit to amplify the signal to the ER        to equalize for the frequency sensitivity of the transducer.    -   G. A digital-to-analog converter (DAC) to convert a digital        audio signal into an analog audio signal for reproduction with        the ER.    -   H. An initialization system to start the SONAR-based headwear        detection platform; which may be manually activated by the user        with voice-activation or with a physical switch, or may be        remotely activated by a second person, or may be automatically        activated by a system which detects when headwear is adjusted or        fitted, or may be activated on a continuous or intermittent        basis.    -   I. A system to generate or retrieve from computer memory a SONAR        audio data test signal. This signal may be one of the following        types:        -   a. Swept sine “chirp” signal.        -   b. Maximum Length Sequence (MLS) test signal.        -   c. Dirac transient click signal.        -   d. Music audio signal.        -   e. Noise signal (white noise or pink noise).    -   J. Circuitry to reproduce the audio test signal in (I) with the        external receiver.    -   K. A system to simultaneously record the ASM signal whilst the        test signal in (I) is reproduced with the ER.    -   L. A system to repeat the reproduction of the test signal in        (I).    -   M. A system to analyze the recorded ASM signal in response to        the SONAR test signal to determine if headwear is worn. This        system comprises a method to deconvolve the recorded ASM signal        to give a time domain impulse response or frequency domain        transfer function with reference to the original SONAR test        audio signal.    -   N. A system to determine if headwear is worn by analysis of the        deconvolved test impulse response (IR) or transfer function (TF)        in (M) with respect to a reference IR or TF made with no        headwear worn.

Another embodiment of the invention enables the HEQS to automaticallydetermine the frequency-dependent acoustic absorption characteristics ofthe headwear worn by a user (this is the Headwear acoustic AttenuationTransmission Index or ATI_HW). Once obtained, the ASM signal is filteredwith a filter corresponding to the inverse of ATI_HW. Thisself-contained SONAR-based headwear determination platform uses a SONARtest sound emitted with an external receiver mounted on the headsetdevice, and its sound reflection is detected using one or more ambientsound microphones mounted on the same headset. The reflected sound isanalyzed to determine the headwear using a look-up table analysis withprevious measurements of known headwear. This SONAR-based headweardetermination platform comprises:

-   -   A. An assembly to monitor the acoustic field in a user's        immediate environment using one or more Ambient Sound        Microphones (ASMs) located near to or at the entrance to one or        both occluded ear canals.    -   B. A signal processing circuit to amplify the signals from the        ASMs in (A) and to equalize for the frequency sensitivity of the        microphones and to low-pass filter (LPF) the signals prior to        digital conversion to prevent aliasing (with the cut-off        frequency of the LPF equal or less than half the sampling        frequency of the digital sampling system).    -   C. An analog-to-digital converter (ADC) to convert the filtered        analog signals in (B) to a digital representation.    -   D. An optional beam-forming platform that takes as its inputs        the digital signals from the ASMs from one or both headsets to        selectively affect the spatial sensitivity of the headset to        sound in the user's local environment.    -   E. An assembly to generate a desired SPL at or near the entrance        to one or both occluded (or partly occluded) ear canals        consisting of a loudspeaker receiver mounted in an earplug that        forms an acoustic seal of the ear canal. (This is the External        Receiver; ER).    -   F. A signal processing circuit to amplify the signal to the ER        to equalize for the frequency sensitivity of the transducer.    -   G. A digital-to-analog converter (DAC) to convert a digital        audio signal into an analog audio signal for reproduction with        the ER.    -   H. An initialization system to start the SONAR-based headwear        detection platform; which may be manually activated by the user        with voice-activation or with a physical switch, or may be        remotely activated by a second person, or may be automatically        activated by a system which detects when headwear is adjusted or        fitted, or may be activated on a continuous or intermittent        basis.    -   I. A system to generate or retrieve from computer memory a SONAR        audio data test signal. This signal may be one of the following        types:        -   a. Swept sine “chirp” signal.        -   b. Maximum Length Sequence (MLS) test signal.        -   c. Dirac transient click signal.        -   d. Music audio signal.        -   e. Noise signal (white noise or pink noise).    -   J. Circuitry to reproduce the audio test signal in (I) with the        external receiver.    -   K. A system to simultaneously record the ASM signal whilst the        test signal in (I) is reproduced with the ER.    -   L. A system to repeat the reproduction of the test signal in        (I).    -   M. A system to analyze the recorded ASM signal in response to        the SONAR test signal to determine if headwear is worn. This        system comprises a method to deconvolve the recorded ASM signal        to give a time domain impulse response or frequency domain        transfer function with reference to the original SONAR test        audio signal.    -   N. A system to determine if headwear is worn by analysis of the        deconvolved test impulse response (IR) or transfer function (TF)        in (M) with respect to a reference IR or TF made with no        headwear worn.    -   O. A system to determine what headwear is worn by the user by        comparing the empirically obtained IR or TR with a library of        measured IRs or TRs previously obtained. The empirically        obtained IR or TR is matched with the particular previously        measured IR or TR using, for example, the method of        least-squared difference.    -   P. A system to obtain the ATI_HW of the worn headwear using a        look-up table of previously measured ATI_HW's corresponding to        particular headwear IR's.    -   Q. A system to filter the ASM signal with a filter corresponding        to the inverse of the obtained ATI_HW. In an exemplary        embodiment, this filter is a digital FIR-type filter.

Another embodiment of the invention enables the HEQS to automaticallydetermine if headwear is worn using a self-contained Voice-basedheadwear detection platform. A Voice test sound is generated by the HEQSuser, and is simultaneously detected using one or more ambient soundmicrophones mounted on the same headset. In some embodiments theuser-generated sound is a non-voice sound such as a hand-clap or mouthwhistle. The measured sound is analyzed to determine the presence ofheadwear. This Voice-based headwear detection platform comprises:

-   -   A. An assembly to monitor the acoustic field in a user's        immediate environment using one or more Ambient Sound        Microphones (ASMs) located near to or at the entrance to one or        both occluded ear canals.    -   B. A signal processing circuit to amplify the signals from the        ASMs in (A) and to equalize for the frequency sensitivity of the        microphones and to low-pass filter (LPF) the signals prior to        digital conversion to prevent aliasing (with the cut-off        frequency of the LPF equal or less than half the sampling        frequency of the digital sampling system).    -   C. An analog-to-digital converter (ADC) to convert the filtered        analog signals in (B) to a digital representation.    -   D. An optional beam-forming platform that takes as its inputs        the digital signals from the ASMs from one or both headsets to        selectively affect the spatial sensitivity of the headset to        sound in the user's local environment.    -   E. A digital-to-analog converter (DAC) to convert a digital        audio signal into an analog audio signal for reproduction with        the ER.    -   F. An initialization system to start the Voice-based headwear        detection platform; which may be manually activated by the user        with voice-activation or with a physical switch, or may be        remotely activated by a second person, or may be automatically        activated by a system which detects when headwear is adjusted or        fitted, or may be activated on a continuous or intermittent        basis.    -   G. A system to obtain a Reference User Voice Profile (rUVP);        when activated by the system in (F), the rUVP acquisition system        works by the user generating some general or predefined verbal        messages (e.g. a collection of phonemically balanced words,        prompted by a messaging system reproduced with the ear canal        receiver). Alternatively, the user may be asked to generate        non-verbal sound stimuli, such as hand claps or mouth-whistles.        Whilst the user creates the Reference sound message, the ASM        signals are simultaneously recorded. The resulting spectral        profile is the rUVP.    -   H. A system to obtain a Current User Voice Profile (cUVP); when        activated by the system in (F), the cUVP acquisition system        works by the user generating some general or predefined verbal        messages (e.g. a collection of phonemically balanced words,        prompted by a messaging system reproduced with the ear canal        receiver). Alternatively, the user may be asked to generate        non-verbal sound stimuli, such as hand claps or mouth-whistles.        Whilst the user creates the Reference sound message, the ASM        signals are simultaneously recorded. The resulting spectral        profile is the cUVP.    -   I. A system to compare the rUVP and cUVP, and thus determine if        headwear is used. This comparison may be in the time domain, but        in an exemplary embodiment the comparison is in the frequency        domain. If the frequency content of the cUVP is less than the        rUVP at particular frequencies (e.g. ⅓^(rd) octave measurements        made at 1 kHz and 4 kHz) by a pre-defined amount (e.g. 5 dB),        then it may be deemed that headwear is currently being worn.

Another embodiment of the invention enables the HEQS to automaticallydetermine the frequency-dependent acoustic absorption characteristics ofthe headwear worn by a user (this is the Headwear acoustic AttenuationTransmission Index or ATI_HW). Once obtained, the ASM signal is filteredwith a filter corresponding to the inverse of ATI_HW. Thisself-contained Voice-based headwear determination platform uses a Voiceor non-voice (e.g. hand-clap) test sound created by the HEQS user, andis simultaneously recorded using one or more ambient sound microphonesmounted on a headset near to or in the user's ear canal. The recordedsound is analyzed to determine the particular headwear and itscorresponding ATI_HW using a look-up table analysis with previousmeasurements of known headwear. This Voice-based headwear determinationplatform comprises:

-   -   A. An assembly to monitor the acoustic field in a user's        immediate environment using one or more Ambient Sound        Microphones (ASMs) located near to or at the entrance to one or        both occluded ear canals.    -   B. A signal processing circuit to amplify the signals from the        ASMs in (A) and to equalize for the frequency sensitivity of the        microphones and to low-pass filter (LPF) the signals prior to        digital conversion to prevent aliasing (with the cut-off        frequency of the LPF equal or less than half the sampling        frequency of the digital sampling system).    -   C. An analog-to-digital converter (ADC) to convert the filtered        analog signals in (B) to a digital representation.    -   D. An optional beam-forming platform that takes as its inputs        the digital signals from the ASMs from one or both headsets to        selectively affect the spatial sensitivity of the headset to        sound in the user's local environment.    -   E. A digital-to-analog converter (DAC) to convert a digital        audio signal into an analog audio signal for reproduction with        the ER.    -   F. An initialization system to start the Voice-based headwear        detection platform; which may be manually activated by the user        with voice-activation or with a physical switch, or may be        remotely activated by a second person, or may be automatically        activated by a system which detects when headwear is adjusted or        fitted, or may be activated on a continuous or intermittent        basis.    -   G. A system to obtain a Reference User Voice Profile (rUVP);        when activated by the system in (F), the rUVP acquisition system        works by the user generating some general or predefined verbal        messages (e.g. a collection of phonemically balanced words,        prompted by a messaging system reproduced with the ear canal        receiver). Alternatively, the user may be asked to generate        non-verbal sound stimuli, such as hand claps or mouth-whistles.        Whilst the user creates the Reference sound message, the ASM        signals are simultaneously recorded. The resulting spectral        profile is the rUVP.    -   H. A system to obtain a Current User Voice Profile (cUVP); when        activated by the system in (F), the cUVP acquisition system        works by the user generating some general or predefined verbal        messages (e.g. a collection of phonemically balanced words,        prompted by a messaging system reproduced with the ear canal        receiver). Alternatively, the user may be asked to generate        non-verbal sound stimuli, such as hand claps or mouth-whistles.        Whilst the user creates the Reference sound message, the ASM        signals are simultaneously recorded. The resulting spectral        profile is the cUVP.    -   I. A system to compare the rUVP and cUVP, and to determine the        particular headwear worn by the user. This comparison may be in        the time domain, but in an exemplary embodiment the comparison        is in the frequency domain. If the frequency content of the cUVP        is less than the rUVP at particular frequencies (e.g. ⅓^(rd)        octave measurements made at 1 kHz and 4 kHz) by a pre-defined        amount (e.g. 5 dB), then it may be deemed that headwear is        currently being worn. The transfer function of rUVP to cUVP is        compared to a database of measurements made with particular        headwear with a known Headwear acoustic Attenuation Transmission        Index or ATI_HW.        Alternative to the ATI_HW determination system in (I), a system        to empirically to determine ATI_HW which is calculated as the        ratio of rUVP to cUVP.    -   J. A system to filter the ASM signal with a filter corresponding        to the inverse of the obtained ATI_HW (i.e. obtained in process        I or J). In the at least one exemplary embodiment, this filter        is a digital FIR-type filter.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions of therelevant exemplary embodiments. Thus, the description of the inventionis merely exemplary in nature and, thus, variations that do not departfrom the gist of the invention are intended to be within the scope ofthe exemplary embodiments of the present invention. Such variations arenot to be regarded as a departure from the spirit and scope of thepresent invention.

What is claimed is:
 1. A device, comprising: a processor that performsoperations, the operations comprising: detecting, based on a change in acharacteristic of an acoustic signal occurring in an acousticenvironment, an acoustical dampening between the acoustic environmentand a microphone; and applying a compensation filter to the acousticsignal to form a compensated acoustic signal that is reproduced.
 2. Thedevice of claim 1, wherein the operations further compriseapproximating, by utilizing the compensation filter, an inverse of theacoustical dampening between the acoustic environment and themicrophone.
 3. The device of claim 1, wherein the operations furthercomprise detecting a presence of headwear communicatively coupled to themicrophone.
 4. The device of claim 3, wherein the operations furthercomprise detecting the presence of the headwear based on an analysis ofthe change in the characteristic of the acoustic signal.
 5. The deviceof claim 1, wherein the operations further comprise determining anacoustic transmission index of headwear communicatively coupled to themicrophone.
 6. The device of claim 1, wherein the operations furthercomprise obtaining an impulse response from headwear communicativelycoupled to the microphone, wherein the impulse response is generated inresponse to a test signal emitted from a receiver of the device.
 7. Thedevice of claim 6, wherein the operations further comprise comparing theimpulse response with measured impulse responses stored in a database tomatch the impulse response with at least one of the impulse responsesstored in the database.
 8. The device of claim 1, wherein the operationsfurther comprise applying the compensation filter based on a transferfunction between the acoustic signal and a reference signal.
 9. Thedevice of claim 8, wherein the operations further comprise determiningthat headwear is worn if the transfer function indicates thathigh-frequency content is attenuated in a voice spectral profile. 10.The device of claim 1, wherein the operations further comprise notapplying the compensation filter if headwear communicatively coupled tothe microphone is determined to not be worn.
 11. The device of claim 1,wherein the operations further comprise predicting if headwearcommunicatively coupled to the microphone is worn.
 12. The device ofclaim 1, wherein the operations further comprise detecting when headwearcoupled to the device is adjusted.
 13. A method, comprising: detecting,by utilizing a processor and based on a change in a characteristic of anacoustic signal occurring in an acoustic environment, an acousticaldampening between the acoustic environment and a microphone of a device;and applying, by utilizing the processor, a compensation filter to theacoustic signal to form a compensated acoustic signal that isreproduced.
 14. The method of claim 13, further comprising detecting anonset of the acoustical dampening.
 15. The method of claim 14, furthercomprising applying the compensation filter in response to the onset ofthe acoustical dampening.
 16. The method of claim 13, further comprisingupdating an acoustic transmission index of headwear communicativelycoupled to the microphone continuously or intermittently.
 17. The methodof claim 16, further comprising terminating the updating if the acoustictransmission index is calculated once.
 18. The method of claim 13,further comprising emitting a test signal from a receiver associatedwith the device.
 19. The method of claim 18, further comprisingreceiving an impulse response from headwear communicatively coupled tothe device in response to the test signal.
 20. A method, comprising:detecting, by utilizing a processor and based on a change in acharacteristic of an acoustic signal occurring in an acousticenvironment, an acoustical dampening between the acoustic environmentand a microphone of a device; and applying, by utilizing the processor,a compensation filter to the acoustic signal to form a compensatedacoustic signal that is reproduced, wherein the compensation filterapproximates an inverse of the acoustical dampening.